diff --git a/library/x509_crt.c b/library/x509_crt.c
index 6d62e44..2f6d924 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -237,7 +237,7 @@
     if (pk_alg == MBEDTLS_PK_ECDSA ||
         pk_alg == MBEDTLS_PK_ECKEY ||
         pk_alg == MBEDTLS_PK_ECKEY_DH) {
-        const mbedtls_ecp_group_id gid = mbedtls_pk_ec(*pk)->grp.id;
+        const mbedtls_ecp_group_id gid = mbedtls_pk_ec_ro(*pk)->grp.id;
 
         if (gid == MBEDTLS_ECP_DP_NONE) {
             return -1;